GCD

index.js

const gcd = (a, b) => {
    if (typeof a !== "number") {
        throw new TypeError(`Expected number, got ${typeof a}`)
    }
    
    if (typeof b !== "number") {
        throw new TypeError(`Expected number, got ${typeof b}`)
    }

    if (b === 0) {
        return a
    }
    
    return gcd(b, a % b)
}

module.exports = input => {
    if (!Array.isArray(input)) {
        throw new TypeError(`Expected an array of numbers, got ${typeof input}`)
    }
    
    if (input.length === 0) {
        return NaN
    }
    
    return input.reduce((previousValue, currentValue) => gcd(previousValue, currentValue))
}